Medicinal plants play an important role in health care throughout the world —especially in non-industrialized continents such as Africa, South America and parts of Asia. Even in many industrialized countries, a number of traditional plants are widely used by a majority of people for minor to moderate everyday ailments through self-medication.
Although many traditional medicinal plant remedies do not undergo extensive scientific testing, they are very popular and their sale is not restricted by government regulatory agencies. Some medicinal plants do have substantial laboratory and clinical testing and those that fall into this category are referred to as phytopharmaceuticals.
One of the major problems associated with phytopharmaceutical plant preparations is the variability in the content of the medicinally active ingredients. This problem was highlighted in Belgium in 1997, when more than 100 people were diagnosed with total destruction of their kidneys through irreversible interstitial fibrosis caused by a mis-identified Chinese medicinal plant (Betz, 1998). This has led to strict government controls on purity and levels of active constituents in phytopharmaceutical products in Europe. Such strict regulation does not currently exist, however, in most countries, including Canada and the United States.
The variability in medicinal content of phytopharmaceutical plants is likely the result of a variety of factors including: year-to-year and plant-to-plant variability in medicinal content; adulteration of medicinal preparations with misidentified plant species; a lack of adequate methods for production and standardization of the crop; a lack of understanding of the unique plant physiology or efficacy with human consumption; and consumer fraud. In addition, phytopharmaceutical plant preparations are typically produced from field-grown crops and therefore are susceptible to infestation by bacteria, fungi and insects that can alter the medicinal content of the preparations.
Past and current efforts have centered on ensuring that preparations of phytopharmaceutical plants contain the correct plant material, that the plant material is processed according to a standardized protocol and that the finished product contains specific levels of a specific marker compound. Another approach has been the application of traditional pharmaceutical development methods to isolate a single “active” component and to synthesize versions of the so-called “drug”. This process usually involves the dissection of the plant into chemical components and attempts to identify a single compound responsible for the induction of the desired effects in mammals. Most phytopharmaceutical plant preparations are formulated from whole plants and contain a variety of compounds which may be working synergistically to produce the desired effect. Although Drug Identification Numbers (DIN) have been issued for various preparations on the basis of a standard concentration of a marker compound, there may be no physiological effect in humans which can be directly attributed to this marker compound. The lack of any real knowledge base for the phytopharmaceutical industry has lead to the current situation in which the sale of phytopharmaceutical plant preparations is driven largely by enthusiasm rather than solid scientific research. Therefore, with the currently available methods, there is no way to ensure quality, efficacy or safety of phytopharmaceutical plant preparations.
Deficiency of trace minerals in humans may occur as the result of inadequate intake of the mineral in the diet or decreased or impaired absorption in the presence of adequate dietary intake (Whittaker, 1998). The problem of mineral deficiency is most prevalent in developing countries where there may be a dietary imbalance in the nutrient composition. It is estimated that more than 2 billion people worldwide suffer from mineral deficiencies, exhibited as common ailments and diseases (for example, zinc deficiency may lead to low fertility; iodine deficiency may be expressed as muscle and thyroid-related ailments; vitamin C deficiencies render susceptibility to common viruses and colds). Factors that decrease or impair the absorption of minerals and nutrients include dietary constituents which as phytate or fiber, drugs or other chemicals that can interact with essential trace minerals and interactions between essential nutrients (Whittaker, 1998).
The conventional approaches to overcome these deficiency-related ailments are dietary supplements (e.g. vitamin C tablets, zinc lozenges), and consumption of fortified food (iron fortified baby foods; vitamin D fortified milk; iodized salt). Foods commonly fortified with mineral nutrients include flour, bakery goods, rice, macaroni products, breakfast cereals and infant formula (Whittaker, 1998). The efficacy of fortification of foods with inorganic mineral compounds, for example Zn(SO4)2, is limited by the low bioavailability of the ions and the high degree of loss through excretion. Recent studies on the bioavailability of fortified nutrients and vitamins in humans have indicated that greater than ⅔ of the nutrients and additives may not be absorbed by the human gastrointestinal system, as they are not in a bioavailable form. In 1993, the Consultant Group on International Agricultural Research (CGIAR) suggested that increasing the mineral uptake of plants could be used to address the problems associated with deficiency of zinc and other nutrients (Ruel and Bouis, 1998).
Echinacea products are currently among the best-selling herbal remedies in North America and have been for several years (Schardt, 1998). Preparations of Echinacea sp. have historically been used for the treatment of common human ailments such as colds and flu (Kindscher, 1992). Commercially prepared extracts and whole dried tissue preparations are made from the root of Echinacea species, a crop which takes about 3 years to produce a saleable product.
Commercial preparations of Echinacea are frequently supplemented with inorganic zinc to increase medicinal efficacy. Zinc supplements are recommended for the maintenance of good health, enhanced immune system function, reduced expression of viral symptoms, tissue formation and for the metabolism of proteins, fats and carbohydrates (Gibson et al., 1998). In commercial preparations, zinc is added to the Echinacea root material during processing in the inorganic form Zn(SO4)2. Therefore the absorbance of the supplemented Zn is limited by the low bioavailablity. Researchers have reported that certain amino acids, cysteine-containing peptides and organic acids, released during digestion may enhance zinc absorption, possibly by forming soluble ligands with zinc or by preventing the formation of the insoluble zinc-phytate complex (Gibson et al., 1998).
Zinc deficiency is one of the leading causes of limited growth rate, loss of appetite, skin lesions, delayed wound healing, hypogonadism, delayed sexual maturation and impaired immune responses in mammals (Whittaker, 1998).
The process of controlling zinc status is a tightly regulated balance of absorption and excretion processes. Zinc is more efficiently absorbed in small amounts than at higher concentrations and other dietary factors such as fiber and phytate inhibit zinc absorption. In addition, the practice of fortifying foods with iron may have a negative impact on zinc status (Whittaker, 1998). Therefore, the recommendations of the American Food and Drug Administration encourage the prudent use of nutrients as supplements to foods but does not encourage the fortification of food staples.
Similarly, zinc fortification of animal feeds is monitored under the guidelines of Agriculture and Agri-Food Canada and limited to less than 250 ppm. In the USA, ongoing research has indicated that supplementation of animal feeds with 3000 ppm inorganic zinc results in more rapid muscle and protein accretion and an overall acceleration in the rate of growth.
One of the most popular medicinal plants in North America is St. John's wort (Hypericum perforatum). In 1998, 7.5 million Americans used St. John's wort for the treatment of neurological disorders and depression (Greenwald, 1998) based on a demonstrated efficacy in numerous clinical trials (Linde et al., 1996). In 1997, the National Institute of Health, Office of Alternative Medicine invested $4.3 million dollars in a 3-year clinical trial to compare the effects of St. John's wort, a placebo and a standard anti-depressive drug in patients suffering from mild depression (NIH, 1997). The standard for St. John's wort preparations is “the whole fresh or dried plant or its components, including not less than 0.04% naphthodianthrones of the hypericin group calculated as hypericin.” (St. John's wort Monograph, 1997) but a recent clinical trial demonstrated that the therapeutic effect of St. John's wort was correlated to the concentration of a second compound hyperforin, (Laakmann et al., 1998). Similar to synthetic antidepressants, the activity of hyperforin was found to cause inhibition of uptake of serotonin, dopamine, noradrenaline, GABA and L-glutamate in animal cell cultures (Chatterjee et al., 1998). Further confounding the situation, studies into the unique physiology of St. John's wort have identified more than 25 additional compounds that may have medicinal activity (Miller, 1998; Nahrstedt and Butterweck, 1997; Evans and Morgenstern, 1997) including the recent report of the presence of relatively high levels of the mammalian neurohormone melatonin (Murch et al., 1997). Therefore, it is clear that the neurological efficacy requires whole plant preparations of St. John's wort.
Lithium, is a mineral element also used in the treatment of depression and neurological disorders. Frequently, traditional pharmaceutical antidepressant therapies can be augmented with lithium in those situations where a patient's depression is either treatment-resistant or partially and/or insufficiently responsive to treatment (Schweitzer & Tuckwell, 1998). Lithium treatment has been used for more than 40 years and has been found to be effective in 60–80% of all patients although the mode of action is not clear. Toxicity of lithium salts can occur when the blood lithium becomes elevated as a result of fever, diabetes, weight loss diets, salt restricted diets or diarrhea.
It is important to solve the problem of the variability in the medicinal content of preparations of phytopharmaceutical plants so that they can be used reliably and effectively. One solution to producing a reliable source of phytopharmaceutical plants is the development and application of in vitro micropropagation procedures to these plants. However, to date, there is no known general method for the in vitro micropropagation of phytopharmaceutical plants.
Furthermore, the phytofortification of phytopharmaceutical plants is desired in order to produce plants that comprise desired additives, nutrients and other compounds of interest that are available in a biocompatible form.
There is, therefore, a need within the phytopharmaceutical plant industry for the development of an in vitro system for the reliable and reproducible propagation of phytopharmaceutical plants, and when desired the phytofortification of phytopharmaceutical plants with desired compounds of interest.
It is an object of the invention to overcome disadvantages of the prior art.
The above object is met by the combinations of features of the main claims, the sub-claims disclose further advantageous embodiments of the invention.